Power supply system

ABSTRACT

A power supply system includes a main line, a plurality of sweep modules, and a control unit. Each sweep module includes a battery module and a power circuit module. The power circuit module switches between connection and disconnection between the battery module and the main line. The control unit executes sweep control for sequentially switching the battery modules which are to be connected to the main line. The control unit maintains connection of a refreshing module which is to be subjected to refreshing charging/discharging to the main line while sweep control is being executed in a state in which the refreshing module is excluded in at least one of outputting of electric power to the outside and inputting of electric power from the outside.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2018-222768 filed on Nov. 28, 2018 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND 1. Technical Field

The disclosure relates to a power supply system including a plurality of modules, each of which includes a battery and a circuit.

2. Description of Related Art

A power supply device that includes a plurality of modules of which each includes a battery and a circuit and performs at least one of outputting of electric power to the outside and storage of electric power which is input from the outside by controlling the plurality of modules is known. For example, a power supply device described in Japanese Patent Application Publication No. 2018-74709 (JP 2018-74709 A) includes a plurality of battery circuit modules of which each includes a battery, a first switching element, and a second switching element. The plurality of battery circuit modules is connected in series with output terminals interposed therebetween. A control circuit of the power supply device outputs a gate signal for switching the first switching element and the second switching element between ON and OFF to the battery circuit modules at intervals of a predetermined time. Accordingly, a target electric power is output from the plurality of battery circuit modules.

SUMMARY

Regarding batteries, it is known that there is a battery in which a charging/discharging capacity is likely to decrease due to an influence of a memory effect (for example, a nickel-hydride battery or a nickel-cadmium battery). In a battery which is likely to be affected by a memory effect, it is preferable to decrease an influence of a memory effect by performing refreshing charging/discharging at an appropriate timing. Refreshing charging/discharging means that at least one of refreshing charging and refreshing discharging is performed. Refresh charging means that a state of charge of a battery is increased to a state of charge with which an influence of a memory effect decreases. Refreshing discharging means that a state of charge of a battery is decreased to a state of charge with which an influence of a memory effect decreases.

In a power supply device including a plurality of modules of which each includes a battery, when a battery which is likely to be affected by a memory effect is used as at least some of the plurality of batteries, it is preferable to perform refreshing charging/discharging. However, in the power supply device described in JP 2018-74709 A, since a plurality of modules of which each includes a battery is connected to each other, it is difficult to efficiently perform refreshing charging/discharging. For example, it is conceivable that refreshing charging/discharging is performed on all batteries in the plurality of modules which are connected to each other. However, in this case, it is necessary to stop a normal operation of the plurality of modules as a whole and thus refreshing charging/discharging is performed on a battery in which it is not necessary to decrease an influence of a memory effect.

The disclosure provides a power supply system that includes a plurality of modules of which each includes a battery and can appropriately perform refreshing charging/discharging.

According to an aspect of the disclosure, there is provided a power supply system including: a main line that supplies electric power which is output to the outside and electric power which is input from the outside; a plurality of sweep modules that is connected to the main line; and a control unit. Each sweep module includes a battery module that includes at least one battery and a power circuit module that includes at least one switching element that switches between connection and disconnection between the battery module and the main line. The control unit is configured to perform a first process of executing sweep control for sequentially switching the battery modules which are to be connected to the main line out of the plurality of battery modules by outputting a gate signal for controlling the switching element to the power circuit module, and a second process of maintaining connection between a refreshing module which is a battery module in which an influence of a memory effect of the battery is to decrease and the main line while performing sweep control in a state in which the refreshing module is excluded in at least one of outputting of electric power to the outside via the main line and inputting of electric power from the outside via the main line.

The power supply system having the above-mentioned configuration executes sweep control for sequentially switching sweep modules which are to be connected to the main line. Here, in the power supply system, connection between a refreshing module which is a battery module in which an influence of a memory effect is to decrease and the main line is maintained, while sweep control is being executed in a state in which the refreshing module is excluded in at least one of outputting of electric power to the outside via the main line and inputting of electric power from the outside via the main line. In this case, when outputting of electric power to the outside via the main line is being performed, refreshing discharging in the refreshing module is appropriately performed in a state in which electric power is being normally output to the outside by the plurality of sweep modules which are subjected to sweep control. When inputting of electric power from the outside via the main line is being performed, refreshing charging of the refreshing module is appropriately performed in a state in which charging of the battery modules in the plurality of sweep modules which are subjected to sweep control is normally being performed. Accordingly, for example, it is not necessary to stop a normal operation of the plurality of sweep modules. Refreshing charging/discharging is not performed on a battery in which an influence of a memory effect does not need to be decreased. Accordingly, with the power supply system having the above-mentioned configuration, refreshing charging/discharging is performed on a battery module in which an influence of a memory effect needs to be decreased.

In the power supply system according to the aspect, the control unit may be configured to execute the sweep control in a state in which the refreshing module in which a state of charge of the battery is increased to a state of charge with which an influence of a memory effect decreases is disconnected from the main line during outputting of electric power to the outside via the main line. In this case, without decreasing a state of charge of a battery module which is to be subjected to refreshing charging, the power supply system can appropriately output electric power to the outside using other sweep modules.

In the power supply system according to the aspect, the control unit may be configured to execute the sweep control in a state in which the refreshing module in which a state of charge of the battery is decreased to a state of charge with which an influence of a memory effect decreases is disconnected from the main line during inputting of electric power from the outside via the main line. In this case, without increasing a state of charge of a battery module which is to be subjected to refreshing discharging, the power supply system can appropriately charge the battery modules of other sweep modules.

In the power supply system according to the aspect, the at least one switching element of the power circuit module may include a first switching element and a second switching element. The first switching element may be attached in series to the main line and in parallel to the battery module. The second switching element may be provided in a circuit that connects the battery module in series to the main line. The control unit may be configured to execute the sweep control by sequentially outputting the gate signal for controlling alternate driving of ON and OFF of the first switching element and the second switching element to a plurality of sweep modules which is to be connected to the main line out of the plurality of sweep modules at intervals of a predetermined delay time, to output a signal for maintaining an OFF state of the first switching element and an ON state of the second switching element to the sweep module including the refreshing module when connection of the refreshing module to the main line is maintained, and to output a signal for maintaining the ON state of the first switching element and the OFF state of the second switching element to the sweep module including the refreshing module when the refreshing module is disconnected from the main line. In this case, sweep control of a plurality of sweep modules and refreshing charging/discharging during sweep control are both appropriately executed.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a diagram schematically illustrating a configuration of a power supply system 1;

FIG. 2 is a diagram schematically illustrating a configuration of a sweep module 20;

FIG. 3 is a timing chart illustrating an example of a sweep operation;

FIG. 4 is a timing chart illustrating an example of a forcible through operation; and

FIG. 5 is a flowchart illustrating a power supply control process which is performed in the power supply system 1.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, an exemplary embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. Details which are not particularly mentioned in this specification and which are required for embodiment can be understood as design details based on the related art by those skilled in the art. The disclosure can be embodied based on details described in this specification and common general technical knowledge in the art. In the following drawings, members and parts performing the same operations will be referred to by the same reference signs. The dimensional relationships in the drawings do not reflect actual dimensional relationships.

<Overall Schematic Configuration>

The overall configuration of a power supply system 1 according to an embodiment will be schematically described below with reference to FIG. 1. The power supply system 1 performs at least one of outputting of electric power to a power distribution device 5 which is connected to a host power system 8 and storage of electric power which is input from the power distribution device 5 (hereinafter simply referred to as “inputting and outputting of electric power”). For example, in this embodiment, a power conditioning subsystem (PCS) is used as the power distribution device 5. The PCS has a function of converting electric power input from the power system 8 to the power supply system 1 or the like and electric power output from the power supply system 1 or the like to the power system 8 between the power supply system 1 or the like and the power system 8.

When electric power is surplus to the power system 8, the power distribution device 5 outputs the surplus electric power to the power supply system 1. In this case, the power supply system 1 stores electric power which is input from the power distribution device 5. The power supply system 1 outputs electric power stored in the power supply system 1 to the power distribution device 5 in accordance with an instruction from a host system 6 that controls the host power system 8. In FIG. 1, the host system 6 is a system that controls the power system 8 and the power distribution device 5 and is provided separately from the power system 8 and the power distribution device 5. However, the host system 6 may be incorporated into the power system 8 or the power distribution device 5.

The power supply system 1 includes one or more strings 10. The power supply system 1 according to this embodiment includes a plurality of (N:N≥2) strings 10 (10A, 10B, . . . , 10N). In FIG. 1, for the purpose of convenience, only two strings 10A and 10B out of the N strings 10 are illustrated. Each string 10 serves as a unit for inputting and outputting electric power to and from the power distribution device 5. The plurality of strings 10 is connected in parallel to the power distribution device 5. Inputting and outputting (power supply) of electric power between the power distribution device 5 and each string 10 is performed via a main line 7.

Each string 10 includes a string control unit (SCU) 11 and a plurality of (M:M≥2) sweep modules 20 (20A, 20B, . . . , 20M). Each sweep module 20 includes a battery and a control circuit. The SCU 11 is provided for each string 10. The SCU 11 is a controller that comprehensively controls the plurality of sweep modules 20 included in the corresponding string 10. Each SCU 11 communicates with a group control unit (GCU) 2 serving as a power control device. The GCU 2 is a controller that comprehensively controls a group including the plurality of strings 10 as a whole. The

GCU 2 communicates with the host system 6 and the SCUs 11. Various methods (for example, at least one of wired communication, wireless communication, and communication via a network) can be employed as a method of communication between the host system 6, the GCU 2, and the SCUs 11.

The configuration of the controllers that control the strings 10, the sweep modules 20, and the like may be modified. For example, the GCU 2 and the SCUs 11 may not be separately provided. That is, one controller may control the whole group including one or more strings 10 and all the plurality of sweep modules 20 included in the string 10.

<Sweep Module>

A sweep module 20 will be described below in detail with reference to FIG. 2. The sweep module 20 includes a battery module 30, a power circuit module 40, and a sweep unit (SU) 50.

The battery module 30 includes at least one battery 31. A plurality of batteries 31 is provided in the battery module 30 according to this embodiment. The plurality of batteries 31 is connected in series. In this embodiment, a secondary battery is used as each battery 31. At least one of various secondary batteries (for example, a nickel-hydride battery, a lithium ion battery, and a nickel-cadmium battery) can be used as the battery 31. In the power supply system 1, a plurality of types of batteries 31 may be mixed. The types of the batteries 31 in all the battery modules 30 may be the same.

A voltage detecting unit 35 and a temperature detecting unit 36 are provided in the battery module 30. The voltage detecting unit 35 detects a voltage of the batteries 31 in the battery module 30 (the plurality of batteries 31 connected in series in this embodiment). The temperature detecting unit 36 detects a temperature of the batteries 31 in the battery module 30 or a temperature near the batteries 31. Various devices (for example, a thermistor) that detect a temperature can be used as the temperature detecting unit 36.

The battery module 30 is provided to be attached to and detached from the power circuit module 40. Specifically, in this embodiment, with the battery module 30 including a plurality of batteries 31 as one unit, detachment of the battery module 30 from the power circuit module 40 and attachment thereof to the power circuit module 40 are performed. Accordingly, in comparison with a case in which the batteries 31 in the battery module 30 are replaced one by one, the number of operation steps when an operator replaces the batteries 31 decreases. In this embodiment, the voltage detecting unit 35 and the temperature detecting unit 36 are replaced separately from the battery module 30. However, at least one of the voltage detecting unit 35 and the temperature detecting unit 36 may be replaced along with the battery module 30.

The power circuit module 40 forms a circuit for appropriately realizing inputting and outputting of electric power in the battery module 30. In this embodiment, the power circuit module 40 includes at least one switching element that switches between connection and disconnection between the battery module 30 and the main line 7. In this embodiment, the power circuit module 40 includes an input and output circuit 43 that connects the battery module 30 to the main line 7 and a first switching element 41 and a second switching element 42 that are provided in the input and output circuit 43. The first switching element 41 and the second switching element 42 perform a switching operation in accordance with a signal (for example, a gate signal) which is input from the sweep unit 50.

In this embodiment, as illustrated in FIG. 2, the first switching element 41 is attached in series to the main line 7 and in parallel to the battery module 30 in the input and output circuit 43. The second switching element 42 is attached to a part of the input and output circuit 43 that connects the battery module 30 in series to the main line 7. A source and a drain of the first switching element 41 are disposed such that a forward direction thereof is set to a direction in which a discharging current flows in the main line 7.

A source and a drain of the second switching element 42 are disposed in the input and output circuit 43 attaching the battery module 30 in series to the main line 7 such that a forward direction thereof is set to a direction in which a charging current flows in the battery module 30. In this embodiment, the first switching element 41 and the second switching element 42 are MOSFETs (for example, Si-MOSFETs) and include body diodes 41 a and 42 a, respectively, set to a forward direction. Here, the body diode 41 a of the first switching element 41 can be appropriately referred to as a first body diode. The body diode 42 a of the second switching element 42 can be appropriately referred to as a second body diode.

The first switching element 41 and the second switching element 42 are not limited to the example illustrated in FIG. 2. Various elements that can switch between connection and disconnection can be used as the first switching element 41 and the second switching element 42. In this embodiment, a MOSFET (specifically an Si-MOSFET) is used as both the first switching element 41 and the second switching element 42. However, an element (for example, a transistor) other than a MOSFET may be employed.

The power circuit module 40 includes an inductor 46 and a capacitor 47. The inductor 46 is provided between the battery module 30 and the second switching element 42. The capacitor 47 is connected in parallel to the battery module 30. In this embodiment, since secondary batteries are used as the batteries 31 of the battery module 30, it is necessary to curb deterioration of the batteries 31 due to an increase in internal resistance loss. Accordingly, by forming an RLC filter using the battery module 30, the inductor 46, and the capacitor 47, equalization of a current is achieved.

A temperature detecting unit 48 is provided in the power circuit module 40. The temperature detecting unit 48 is provided to detect emission of heat from at least one of the first switching element 41 and the second switching element 42. In this embodiment, the first switching element 41, the second switching element 42, and the temperature detecting unit 48 are assembled into one base. Accordingly, the base is replaced at a time point at which a defect of one of the first switching element 41 and the second switching element 42 has been detected. Accordingly, in this embodiment, by providing one temperature detecting unit 48 near the first switching element 41 and the second switching element 42, it is possible to decrease the number of components. Here, a temperature detecting unit that detects the temperature of the first switching element 41 and a temperature detecting unit that detects the temperature of the second switching element 42 may be provided separately from each other. Various devices (for example, a thermistor) that detect a temperature can be used as the temperature detecting unit 48.

As illustrated in FIGS. 1 and 2, a plurality of battery modules 30 in the string 10 are connected in series to the main line 7 with the corresponding power circuit modules 40 interposed therebetween. By appropriately controlling the first switching element 41 and the second switching element 42 of each power circuit module 40, the corresponding battery module 30 is connected to the main line 7 or is disconnected from the main line 7. In the example of the configuration of the power circuit module 40 illustrated in FIG. 2, when the first switching element 41 is turned off and the second switching element 42 is turned on, the battery module 30 is connected to the main line 7. When the first switching element 41 is turned on and the second switching element 42 is turned off, the battery module 30 is disconnected from the main line 7.

The sweep unit (SU) 50 is a control unit that is incorporated into the sweep module 20 such that various controls associated with the sweep module 20 are executed, and is also referred to as a sweep control unit. Specifically, the sweep unit 50 outputs a signal for driving the first switching element 41 and the second switching element 42 in the power circuit module 40. The sweep unit 50 notifies a host controller (the SCU 11 illustrated in FIG. 1 in this embodiment) of states of the sweep module 20 (for example, the voltage of the battery module 30, the temperature of the batteries 31, and the temperature of the switching elements 41 and 42). The sweep unit 50 is incorporated into each of a plurality of sweep modules 20 of each string 10. The sweep units 50 incorporated into the plurality of sweep modules 20 of each string 10 are sequentially connected to each other and are configured to allow a gate signal GS which is output from the SCU 11 to propagate sequentially. As illustrated in FIG. 2, in this embodiment, each sweep unit 50 includes an SU processing unit 51, a delay/selection circuit 52, and a gate driver 53.

The SU processing unit 51 is a controller that takes charge of various processes in the sweep unit 50. For example, a microcomputer can be used as the SU processing unit 51. Detection signals from the voltage detecting unit 35, the temperature detecting unit 36, and the temperature detecting unit 48 are input to the SU processing unit 51. The SU processing unit 51 performs inputting and outputting various signals to and from a host controller (the SCU 11 of the string 10 in this embodiment).

The signals which are input from the SCU 11 to the SU processing unit 51 include a forcible through signal CSS and a forcible connection signal CCS. The forcible through signal CSS is a signal for instructing to disconnect the battery module 30 from the main line 7 (see FIG. 1) extending from the power distribution device 5 to the string 10. That is, the sweep module 20 to which the forcible through signal CSS is input ignores an operation for inputting and outputting electric power to and from the power distribution device 5. The forcible connection signal CCS is a signal for instructing to maintain connection of the battery module 30 to the main line 7.

A gate signal GS is input to the delay/selection circuit 52. The gate signal (a PWM signal in this embodiment) GS is a signal for controlling an alternate repeated switching operation between an ON state and an OFF state of the first switching element 41 and the second switching element 42. The gate signal GS is a pulse-shaped signal in which ON and OFF are alternately repeated. The gate signal GS is first input to the delay/selection circuit 52 in one sweep module 20 from the SCU 11 (see FIG. 1). Subsequently, the gate signal GS propagates sequentially from the delay/selection circuit 52 of one sweep module 20 to the delay/selection circuit 52 of another sweep module 20.

In each string 10, sweep control which is illustrated in FIGS. 3 and 4 is executed. Here, FIG. 3 is a timing chart illustrating an example of a sweep operation.

Specifically, in FIG. 3, a relationship between a connection state of the sweep modules 20 and a voltage output to the power distribution device 5 when all the sweep modules 20 execute the sweep operation is illustrated as an example. FIG. 4 is a timing chart illustrating an example of a forcible through operation. Specifically, in FIG. 4, a relationship between a connection state of the sweep modules 20 and a voltage output to the power distribution device 5 when some sweep modules 20 execute the forcible through operation is illustrated as an example.

In sweep control which is executed in each string 10, the number m of sweep modules 20 which are turned on at the same time out of a plurality of (for example,

M) sweep modules 20 incorporated into the string 10 is determined. The gate signal GS in sweep control has, for example, a pulse-shaped waveform. In the gate signal GS, for example, a signal waveform for connecting the battery module 30 to the main line 7 and a signal waveform for disconnecting the battery module 30 from the main line 7 may be sequentially disposed. In the gate signal GS, the signal waveform for connecting the battery module 30 to the main line 7 has only to embed the number of battery modules 30 which are connected to the main line 7 in a predetermined period T in which the string 10 is swept. The signal waveform for disconnecting the battery module 30 from the main line 7 has only to embed the number of battery modules 30 which are to be disconnected from the main line 7 out of the battery modules 30 incorporated into the string 10. In the signal waveform for connecting the battery module 30 to the main line 7 and the signal waveform for disconnecting the battery module 30 from the main line 7, wavelengths thereof and the like are appropriately adjusted.

In each string 10 according to this embodiment, M sweep modules 20 are connected in series in the order of sweep modules 20A, 20B, . . . , 20M from the power distribution device 5. In the following description, a side which is close to the power distribution device 5 is defined as an upstream side, and a side which is distant from the power distribution device 5 is defined as a furthest downstream side. First, the gate signal GS is input from the SCU 11 to the delay/selection circuit 52 of the sweep unit 50 in the sweep module 20A which is upstream. Subsequently, the gate signal GS propagates from the delay/selection circuit 52 of the sweep module 20A to the delay/selection circuit 52 of the sweep module 20B adjacent thereto downstream. Propagation of the gate signal to the sweep module 20 adjacent thereto downstream is sequentially repeated up to the sweep module 20M which is furthest downstream.

Here, the delay/selection circuit 52 can allow a pulse-shaped gate signal GS which is input from the SCU 11 or the upstream sweep module 20 to propagate to the downstream sweep module 20 with a delay of a predetermined delay time. In this case, a signal indicating the delay time is input from the SCU 11 to the sweep unit 50 (the SU processing unit 51 in the sweep unit 50 in this embodiment). The delay/selection circuit 52 delays the gate signal GS based on the delay time indicated by the signal. The delay/selection circuit 52 may allow the input gate signal GS to propagate to the downstream sweep module 20 without a delay.

The gate driver 53 drives the switching operations of the first switching element 41 and the second switching element 42. The delay/selection circuit 52 outputs a signal for controlling driving of the gate driver 53 to the gate driver 53. The gate driver 53 outputs control signals to the first switching element 41 and the second switching element 42. When the battery module 30 is to be connected to the main line 7, the gate driver 53 outputs a control signal for turning off the first switching element 41 and turning on the second switching element 42. When the battery module 30 is disconnected from the main line 7, the gate driver 53 outputs a control signal for turning on the first switching element 41 and the turning off the second switching element 42.

The delay/selection circuit 52 in this embodiment is controlled by a controller such as the SCU 11 and selectively performs a sweep operation, a forcible through operation, and a forcible connection operation.

For example, in the sweep operation, the first switching element 41 and the second switching element 42 are operated by the gate signal GS. A plurality of battery modules 30 included in the string 10 are connected to the main line 7 in a predetermined order and is disconnected from the main line 7 in a predetermined order. As a result, the string 10 is driven such that a predetermined number of battery modules 30 are normally connected to the main line 7 while sequentially changing the battery modules 30 connected to the main line 7 in a short control cycle. Through this sweep operation, the string 10 serves as one battery pack in which the predetermined number of battery modules 30 are connected in series while sequentially changing the battery modules 30 connected to the main line 7 in the short control cycle. The sweep modules 20 of the string 10 are controlled by the SCU 11 such that such a sweep operation is realized. In this control, the SCU 11 outputs the gate signal GS to the string 10 and outputs the control signal to the SU processing unit 51 incorporated into the sweep module 20. Details of an example of the sweep operation will be described later with reference to FIGS. 3 and 4.

In the sweep operation, the delay/selection circuit 52 outputs the input gate signal GS to the gate driver 53 without any change and causes the gate signal GS to propagate to a downstream sweep module 20 with a delay of a delay time. As a result, the battery modules 30 of the sweep modules 20 under the sweep operation are sequentially connected to the main line 7 and are sequentially disconnected from the main line 7 at different timings in the string 10.

In the forcible through operation, the delay/selection circuit 52 outputs a signal for maintaining the first switching element 41 in the ON state and maintaining the second switching element 42 in the OFF state to the gate driver 53 regardless of the input gate signal GS. As a result, the battery modules 30 of the sweep modules 20 under the forcible through operation are disconnected from the main line 7. The delay/selection circuit 52 of the sweep module 20 under the forcible through operation causes the gate signal GS to propagate the downstream sweep module 20 without a delay.

In the forcible connection operation, the delay/selection circuit 52 outputs a signal for maintaining the first switching element 41 in the OFF state and maintaining the second switching element 42 in the ON state to the gate driver 53 regardless of the input gate signal GS. As a result, the battery modules 30 of the sweep modules 20 under the forcible connection operation are normally connected to the main line 7. The delay/selection circuit 52 of the sweep module 20 under the forcible connection operation causes the gate signal GS to propagate the downstream sweep module 20 without a delay.

The delay/selection circuit 52 may be constituted as a single integrated circuit that performs the above-mentioned necessary functions. The delay/selection circuit 52 may be constituted in combination between a circuit that delays a gate signal GS and a circuit that selectively outputs a gate signal GS to the gate driver 53. An example of the configuration of the delay/selection circuit 52 in this embodiment will be described below.

In this embodiment, as illustrated in FIG. 2, the delay/selection circuit 52 includes a delay circuit 52 a and a selection circuit 52 b. The gate signal GS input to the delay/selection circuit 52 is input to the delay circuit 52 a. The delay circuit 52 a outputs the gate signal GS to the selection circuit 52 b with a delay of a predetermined delay time. The gate signal GS input to the delay/selection circuit 52 is output to the selection circuit 52 b via another route which does not pass through the delay circuit 52 a without any change. The selection circuit 52 b receives an instruction signal from the SU processing unit 51 and outputs the gate signal GS in accordance with the instruction signal.

When the instruction signal from the SU processing unit 51 instructs to perform a sweep operation, the selection circuit 52 b outputs the input gate signal GS to the gate driver 53 of the sweep module 20 without any change. The gate driver 53 outputs a control signal to the power circuit module 40, turns off the first switching element 41, turns on the second switching element 42, and connects the battery module 30 to the main line 7.

On the other hand, the selection circuit 52 b outputs the gate signal GS with a delay to the delay/selection circuit 52 of the sweep module 20 adjacent thereto downstream. That is, when the battery module 30 is connected to the main line 7 in the sweep operation, the gate signal GS with a delay of a predetermined delay time is sent to the sweep module 20 adjacent thereto downstream.

When the instruction signal from the SU processing unit 51 is the forcible through signal CSS, the selection circuit 52 b outputs a signal for ignoring the battery module 30 to the gate driver 53. By maintaining the forcible through signal CSS, the battery module 30 of the sweep module 20 receiving the forcible through signal CSS is maintained in a state in which it is disconnected from the main line 7. In this case, the selection circuit 52 b outputs the gate signal GS, which is input to the selection circuit 52 b via another route which does not pass through the delay circuit 52 a, to the sweep module 20 adjacent thereto downstream.

When the instruction signal from the SU processing unit 51 is the forcible connection signal CCS, the selection circuit 52 b outputs a signal for connecting the battery module 30 to the main line 7 to the gate driver 53. That is, the gate driver 53 turns off the first switching element 41, turns on the second switching element 42, and connects the battery module 30 to the main line 7. By maintaining the forcible connection signal CCS, the battery module 30 is maintained in a state in which it is connected to the main line 7.

In this case, the selection circuit 52 b outputs the gate signal GS, which is input to the selection circuit 52 b via another route which does not pass through the delay circuit 52 a, to the sweep module 20 adjacent thereto downstream.

As illustrated in FIGS. 1 and 2, in this embodiment, a plurality of sweep units 50 (specifically a plurality of delay/selection circuits 52) included in one string 10 is sequentially connected in a daisy chain manner. As a result, the gate signal GS input from the SCU 11 to one sweep unit 50 propagates sequentially to the plurality of sweep units 50. Accordingly, processes in the SCU 11 are likely to be simplified and an increase in signal properties is easily curbed. However, the SCU 11 may individually output the gate signal GS to the plurality of sweep units 50.

Each sweep unit 50 includes an indicator 57. The indicator 57 notifies an operator of, for example, a state of the sweep module 20 including a battery module 30 or a power circuit module 40. The indicator 57 can notify an operator, for example, that a defect in the battery module 30 of the sweep module 20 (for example, failure or deterioration of the batteries 31) has been detected (that is, the battery module 30 should be replaced).

For example, an LED which is a kind of light emitting device is used as the indicator 57 in this embodiment. However, a device (for example, a display) other than an LED may be used as the indicator 57. A device (for example, a speaker) that outputs voice may be used as the indicator 57. The indicator 57 may notify an operator of the state of the sweep module 20 by driving a member using an actuator (for example, a motor or a solenoid). The indicator 57 may be configured to indicate the state using different methods depending on the state of the sweep module 20.

In this embodiment, the operation of the indicator 57 is controlled by the SU processing unit 51 of the sweep unit 50. However, a controller (for example, the SCU 11) other than the SU processing unit 51 may control the operation of the indicator 57.

In this embodiment, the indicator 57 is provided for each sweep unit 50. Accordingly, an operator can easily identify the sweep module 20 of which the state has been notified by the indicator 57 out of the plurality of sweep modules 20 which are arranged. However, the configuration of the indicator 57 may be modified. For example, separately from the indicator 57 disposed for each sweep unit 50 or along with the indicator 57, a state notifying unit that notifies the states of a plurality of sweep modules 20 in a bundle may be provided. In this case, for example, the state notifying unit may display the states of the plurality of sweep modules 20 (for example, whether a defect has occurred) on one monitor.

<Sweep Control>

Sweep control which is executed in a string 10 will be described below. Here, sweep control is control for causing each battery module 30 of the string 10 to perform a sweep operation. In sweep control which is executed in the string 10, the SCU 11 outputs a pulse-shaped gate signal GS. The switching elements 41 and 42 in a plurality of sweep modules 20 of the string 10 are driven to switch appropriately between ON and OFF. As a result, connection of the battery module 30 to the main line 7 and disconnection of the battery module 30 from the main line 7 are fast switched to each other for each sweep module 20. In the string 10, the gate signal GS which is input to an X-th sweep module 20 from upstream can be delayed with respect to the gate signal GS which is input to an (X−1)-th sweep module 20. As a result, m (m<M) sweep modules 20 connected to the main line 7 out of M sweep modules 20 in the string 10 are sequentially switched. Accordingly, a plurality of battery modules 30 included in the string 10 is connected to the main line 7 in a predetermined order and is disconnected from the main line in a predetermined order. A predetermined number of battery modules 30 can be normally connected to the main line 7. Through this sweep operation, the string 10 serves as a single battery pack in which a predetermined number of battery modules 30 are connected in series.

FIG. 3 is a timing chart illustrating an example of a relationship between connection states of sweep modules 20 and a voltage which is output to the power distribution device 5 when all the sweep modules 20 included in the string 10 are caused to perform the sweep operation. The number M of sweep modules 20 included in one string 10 can be appropriately changed. In the example illustrated in FIG. 3, five sweep modules 20 are included in one string 10 and all of the five sweep modules 20 are caused to perform the sweep operation.

In the example illustrated in FIG. 3, a VH command signal for setting a voltage VH [V] output to the power distribution device 5 to 100 V is input to the SCU 11 of the string 10. The voltage Vmod [V] of the battery module 30 in each sweep module 20 is 43.2 V. The delay time DL [μsec] by which a gate signal GS is delayed is appropriately set depending on the specification required for the power supply system 1. The period T of the gate signal GS (that is, the period in which a sweep module 20 is connected and disconnected) has a value which is obtained by multiplying the delay time DL by the number P of sweep modules 20 (≤M) which are to perform the sweep operation. Accordingly, when the delay time DL is set to be greater, the frequency of the gate signal GS becomes lower. On the other hand, when the delay time DL is set to be less, the frequency of the gate signal GS becomes higher. In the example, illustrated in FIG. 3, the delay time DL is set to 2.4 μsec. Accordingly, the period T of the gate signal GS is “2.4 μsec×5=12 μsec.”

In this embodiment, a battery module 30 of a sweep module 20 in which the first switching element 41 is turned off and the second switching element 42 is turned on is connected to the main line 7. That is, when the first switching element 41 is turned off and the second switching element 42 is turned on, the capacitor 47 that is provided in parallel to the battery module 30 is connected to the input and output circuit 43 and electric power is input and output. The sweep unit 50 of the sweep module 20 connects the battery module 30 to the main line 7 while the gate signal GS is in the ON state. On the other hand, a battery module 30 of a sweep module 20 in which the first switching element 41 is turned on and the second switching element 42 is turned off is disconnected from the main line 7. The sweep unit 50 disconnects the battery module 30 from the main line 7 while the gate signal GS is in the OFF state.

When the first switching element 41 and the second switching element 42 are simultaneously turned on, a short-circuit occurs. Accordingly, when the first switching element 41 and the second switching element 42 are driven to switch, the sweep unit 50 switches one element from ON to OFF and switches the other element from OFF to ON after a slightly waiting time has elapsed thereafter. As a result, it is possible to prevent a short-circuit from occurring.

A VH command value which is instructed by a VH command signal is defined as VH_com, a voltage of each battery module 30 is defined as Vmod, and the number of sweep modules 20 which are to perform the sweep operation (that is, the number of sweep modules 20 which are to be connected to the main line 7 in sweep control) is defined as P. In this case, a duty ratio of an ON time to the period T in a gate signal GS is calculated as VH_com/(Vmod×P). In the example illustrated in FIG. 3, the duty ratio of the gate signal GS is about 0.46. Strictly, the duty ratio varies due to an influence of the waiting time for preventing occurrence of a short-circuit. Accordingly, the sweep unit 50 may perform correction of the duty ratio using a feedback process or a feedforward process.

As illustrated in FIG. 3, when sweep control is started, first, one of P sweep modules 20 (the sweep module 20 of No. 1 which is furthest upstream in the example illustrated in FIG. 3) is connected. Thereafter, when the delay time DL elapses, a next sweep module 20 (the sweep module 20 of No. 2 which is located the second from upstream in the example illustrated in FIG. 3) is connected. In this state, the voltage VH which is output to the power distribution device 5 is a sum value of the voltages of two sweep modules 20 and does not reach the VH command value. When the delay time DL elapses additionally, the sweep module 20 of No. 3 is connected. In this state, the number of sweep modules 20 connected to the main line 7 is three of Nos. 1 to 3. Accordingly, the voltage VH which is output to the power distribution device 5 is a sum value of the voltages of three sweep modules 20 and is greater than the VH command value.

Thereafter, when the sweep module 20 of No. 1 is disconnected from the main line 7, the voltage VH returns to the sum value of the voltages of two sweep modules 20. When the delay time DL elapses after the sweep module of No. 3 has been connected, the sweep module 20 of No. 4 is connected. As a result, the number of sweep modules 20 which are connected to the main line 7 through sweep control are three of Nos. 2 to 4. As described above, m (three in FIG. 3) sweep modules 20 which are connected to the main line 7 out of M (five in FIG. 3) sweep modules 20 are sequentially switched.

As illustrated in FIG. 3, the VH command value may not be indivisible by the voltage Vmod of each battery module 30. In this case, the voltage VH which is output to the power distribution device 5 varies. However, the voltage VH is equalized by the

RLC filter and is output to the power distribution device 5. Even when the battery modules 30 of the sweep modules 20 are charged with electric power which is input from the power distribution device 5, the connection states of the sweep modules 20 are controlled similarly to the timing chart illustrated in FIG. 3.

<Forcible Through Operation>

Control when some sweep modules 20 are caused to perform a forcible through operation and the other sweep modules 20 are caused to perform a sweep operation will be described below with reference to FIG. 4. As described above, the sweep module 20 which has been instructed to perform a forcible through operation maintains a state in which the battery module 30 is disconnected from the main line 7.

The example illustrated in FIG. 4 is different from the example illustrated in FIG. 3 in that the sweep module 20 of No. 2 is caused to perform a forcible through operation. That is, in the example illustrated in FIG. 4, the number P of sweep modules 20 which are caused to perform a sweep operation (that is, the number of sweep modules 20 which are to be connected to the main line 7) out of five sweep modules 20 included in one string 10 is four. The VH command value, the voltage Vmod of each battery module 30, and the delay time DL are the same as in the example illustrated in FIG. 3. In the example illustrated in FIG. 4, the period T of the gate signal GS is “2.4 μsec×4=9.6 μsec.” The duty ratio of the gate signal GS is about 0.58.

As illustrated in FIG. 4, when some sweep modules 20 (the sweep module 20 of No. 2 in FIG. 4) are caused to perform a forcible through operation, the number P of sweep modules 20 which are caused to perform a sweep operation is less than that in the example illustrated in FIG. 3. However, the string 10 adjusts the period T of the gate signal GS and the duty ratio of the gate signal GS with the decrease in the number P of sweep modules 20 which are caused to perform a sweep operation. As a result, the waveform of the voltage VH which is output to the power distribution device 5 is the same as the waveform of the voltage VH illustrated in FIG. 3. Accordingly, the string 10 can appropriately output the commanded voltage VH to the power distribution device 5 even when the number P of sweep modules 20 which are caused to perform a sweep operation is increased or decreased.

For example, when a defect (for example, deterioration or failure) occurs in a battery 31 in a certain sweep module 20, the string 10 can cause the sweep module 20 including the battery 31 in which a defect has occurred to perform a forcible through operation. Accordingly, the string 10 can appropriately output the commanded voltage

VH to the power distribution device 5 using the sweep modules 20 in which a defect has not occurred. An operator can replace the battery module 30 including the battery 31 in which a defect has occurred (that is, the battery module 30 of the sweep module 20 which is performing a forcible through operation) in a state in which the string 10 is operating normally. In other words, in the power supply system 1 according to this embodiment, it is not necessary to stop the operation of the string 10 as a whole when a battery module 30 is replaced.

When a certain sweep module 20 is caused to perform a forcible connection operation, the connection state of the sweep module 20 which is caused to perform a forcible connection operation is a normally connected state. For example, when the sweep module 20 of No. 2 in FIG. 4 is caused to perform a forcible connection operation instead of a forcible through operation, the connection state of No. 2 is maintained in a “connected state” instead of a “disconnected state.”

When the power supply system 1 includes a plurality of strings 10, the above-mentioned sweep control is executed in each of the plurality of strings 10. The controller (the GCU 2 in this embodiment) that comprehensively controls the power supply system 1 as a whole controls the operations of the plurality of strings 10 such that a command from the host system 6 is satisfied. For example, when a VH command value required from the host system 6 cannot be satisfied by only one string 10, the GCU 2 may satisfy the VH command value by causing the plurality of strings 10 to output electric power.

<String>

The entire configurations of the string 10 and the power supply system 1 will be described below in detail with reference to FIG. 1. As described above, the string 10 includes an SCU 11 and a plurality of sweep modules 20 that is connected in series to the main line 7 with a power circuit module 40 interposed therebetween. The main line 7 of the string 10 is connected to a bus line 9 extending from the power distribution device 5. The string 10 includes a bus line voltage detecting unit 21, a system breaker (this system breaker is appropriately referred to as a “system main relay (SMR)”) 22, a string capacitor 23, a string current detecting unit 24, a string reactor 25, and a string voltage detecting unit 26 sequentially from the power distribution device 5 side (upstream) in the main line 7. Disposition of some members may be modified. For example, the system breaker 22 may be provided downstream from the string capacitor 23.

The bus line voltage detecting unit 21 detects a voltage of the bus line 9 extending from the power distribution device 5 to the string 10. The system breaker 22 switches between connection and disconnection between the string 10 and the power distribution device 5. In this embodiment, the system breaker 22 is driven in accordance with a signal which is input from the SCU 11. The string capacitor 23 and the string reactor 25 form an RLC filter to achieve equalization of a current. The string current detecting unit 24 detects a current flowing between the string 10 and the power distribution device 5. The string voltage detecting unit 26 detects a total voltage of voltages of the plurality of sweep modules 20 which is connected in series to the main line 7 in the string 10, that is, a string voltage of the string 10.

In the example illustrated in FIG. 1, the system breaker 22 includes a switch 22 a and a fuse 22 b. The switch 22 a is a device that connects or disconnects the string 10 to and from the power distribution device 5. The switch 22 a can be appropriately referred to as a string switch. By turning on the switch 22 a, the main line 7 of the string 10 is connected to the bus line 9 of the power distribution device 5. By turning off the switch 22 a, the string 10 is disconnected from the power distribution device 5. The switch 22 a is controlled by the SCU 11 controlling the string 10. By operating the switch 22 a, the string 10 can be appropriately disconnected from or connected to the power distribution device 5. The fuse 22 b is a device that stops an unexpected large current when the large current flows in the main line 7 of the string 10 in view of design of the string 10. The fuse 22 b is also appropriately referred to as a string fuse.

Here, when batteries incorporated into one battery module 30 have the same standard, the voltage of one battery module 30 increases as the number of batteries incorporated increases. On the other hand, when the voltage of one battery module 30 is high, the battery module is dangerous for an operator to handle and is heavy. In this regard, as many batteries as possible may be incorporated into one battery module 30 within a range of a voltage with which an operator will not be subjected to a significant accident even with touch of the operator with the fully charged battery module (for example, lower than 60 V and preferably lower than 42 V) and within a range of a weight with which an operator can easily replace the battery module. The battery module 30 which is incorporated into the string 10 does not need to include the same batteries, and the number of batteries which are incorporated into one battery module 30 can be determined depending on types, standards, or the like of the batteries which are incorporated into the battery module 30. The string 10 is configured to output a necessary voltage by combining sweep modules 20 into which the battery module 30 has been incorporated in series. The power supply system 1 is configured to output electric power required for connection to the power system 8 by combining a plurality of strings 10.

In this embodiment, the power distribution device 5 to which a plurality of strings 10 of the power supply system 1 is connected includes sub power distribution devices 5A and 5B that are connected to the strings 10A and 10B. The strings 10A and 10B connected to the sub power distribution devices 5A and 5B are connected in parallel via the sub power distribution devices 5A and 5B. The power distribution device 5 controls distribution of electric power which is input to the strings 10A and 10B from the power system 8, combination of electric power which is output from the strings 10A and 10B to the power system 8, and the like through the sub power distribution devices 5A and 5B connected to the strings 10. The power distribution device 5 and the sub power distribution devices 5A and 5B are controlled such that the power supply system 1 into which a plurality of strings 10 is incorporated serves as a single power supply device as a whole by cooperation between the GCU 2 connected to the host system 6 and the SCU 11 that controls each string 10.

For example, in this embodiment, a downstream side from the power distribution device 5, that is, the strings 10A and 10B side, is controlled with a direct current. An upstream side from the power distribution device 5, that is, the power system 8, is controlled with an alternating current. The voltages of the strings 10A and 10B are controlled to be roughly balanced with the voltage of the power system 8 via the power distribution device 5. When the voltage of each of the strings 10A and 10B is controlled to be lower than that of the power system 8, a current flows from the power system 8 to each of the strings 10A and 10B. At this time, when sweep control is executed in the strings 10A and 10B, the battery modules 30 are appropriately charged. When the voltage of each of the strings 10A and 10B is controlled to be higher than that of the power system 8, a current flows from each of the strings 10A and 10B to the power system 8. At this time, when sweep control is executed in the strings 10A and 10B, the battery modules 30 are appropriately discharged. The power distribution device 5 may maintain the voltages of the strings 10A and 10B to be equal to the voltage of the power system 8 such that a current hardly flows in the strings 10A and 10B. In this embodiment, this control can be executed for each of the sub power distribution devices 5A and 5B to which the strings 10A and 10B are connected. For example, by adjusting the voltage for each of the strings 10A and 10B, control may be executed such that a current hardly flows in some string 10 out of a plurality of strings 10A and 10B connected to the power distribution device 5.

In the power supply system 1, the total capacity of the power supply system 1 can be increased by increasing the number of strings 10 which are connected in parallel to the power distribution device 5. For example, with the power supply system 1, it is possible to construct a large system that can output electric power such that a sudden increase in demand in the power system 8 can be absorbed or can supplement sudden power shortage in the power system 8. For example, by increasing the capacity of the power supply system 1, great surplus electric power of the power system 8 can be appropriately transferred to charging of the power supply system 1. For example, when output power of a power plant is surplus in a night time zone in which demand for electric power is low or when an amount of electric power generated in a large photovoltaic system increases suddenly, the power supply system 1 can absorb surplus electric power via the power distribution device 5. On the other hand, when demand for electric power in the power system 8 increases suddenly, necessary electric power can be appropriately output from the power supply system 1 to the power system 8 via the power distribution device 5 in accordance with a command from the host system 6. Accordingly, with the power supply system 1, power shortage in the power system 8 is appropriately supplemented.

In the power supply system 1, it is not necessary to normally connect all battery modules 30 out of a plurality of battery modules 30 which is incorporated into a string 10. Since a forcible through operation can be performed for each battery module 30 as described above, a battery module 30 in which a defect has occurred can be disconnected from sweep control of the string 10 when a defect has occurred in the battery module 30. Accordingly, in the power supply system 1, a battery which is used for the battery module 30 does not need to be a new battery which has not been used.

For example, a secondary battery which has been used as a driving power source of a motor-driven vehicle such as a hybrid vehicle or an electric vehicle can be appropriately reused. Even when such a secondary battery which has been used as a driving power source is used, for example, for about 10 years, the secondary battery can satisfactorily perform a secondary battery function. In the power supply system 1, since a battery module 30 in which a defect has occurred can be immediately disconnected, a battery can be incorporated into the battery module 30, for example, by ascertaining that the battery performs a necessary function. The time for sequentially recovering a secondary battery which has been used as a driving power source of a motor-driven vehicle comes up. With the power supply system 1, for example, secondary batteries corresponding to 10,000 motor-driven vehicles may be incorporated thereinto and thus considerable recovered secondary batteries can be absorbed. It cannot be seen when a secondary battery which has been used as a driving power source of a motor-driven vehicle deteriorates in performance. When such a secondary battery is reused for a battery module 30 of the power supply system 1, it is not possible to predict when a defect occurs in the battery module 30.

With the power supply system 1 which has been proposed herein, it is possible to appropriately disconnect a battery module 30 via a sweep module 20. Accordingly, even when a defect occurs suddenly in a battery module 30 or a secondary battery incorporated into the battery module 30, it is not necessary to stop the power supply system 1 as a whole.

<Refreshing Charging/Discharging>

Although details will be described later, the power supply system 1 according to this embodiment can perform refreshing charging/discharging for each battery module 30 while executing sweep control which is illustrated in FIGS. 3 and 4. That is, the power supply system 1 according to this embodiment can perform refreshing charging/discharging on certain battery modules 30 of the string 10 while performing a general discharging or charging operation which is commanded from the host system 6 through sweep control in the overall string 10. Refreshing charging/discharging means that at least one of refreshing charging and refreshing discharging is performed. Refresh charging means that a state of charge of a battery is increased to a state of charge with which an influence of a memory effect decreases. Refreshing discharging means that a state of charge of a battery is decreased to a state of charge with which an influence of a memory effect decreases.

A method of determining a battery module 30 which is subjected to refreshing charging/discharging and details of refreshing charging/discharging can be appropriately set depending on various conditions. For example, a control unit (the SCU 11 in this embodiment) may determine a battery module 30 which is to be subjected to refreshing charging/discharging and details of refreshing charging/discharging for each battery module 30 based on at least one of a type of the battery 31 which is used for the battery module 30, a charging frequency and a discharging frequency of the battery module 30, a voltage, a temperature, and a state of charge (SOC), an SOC range in a normal state, an open circuit voltage (OCV), and a relationship between a voltage and an amount of electric power discharge at the time of discharging.

For example, details of refreshing charging/discharging may include at least one of whether both refreshing charging and refreshing discharging are to be performed, whether only refreshing charging is to be performed, whether only refreshing discharging is to be performed, an amount of electric power with which the battery module 30 which is subjected to refreshing charging is charged, an amount of electric power discharged from the battery module 30 which is subjected to refreshing discharging, the number of times of refreshing charging/discharging, and a waiting time from completion of refreshing charging/discharging to restart of use of the battery module 30.

As described above, the batteries 31 of all the battery modules 30 in the power supply system 1 according to this embodiment may be of the same type or a plurality of types of batteries 31 may be mixed. Refreshing charging/discharging is preferably performed on a battery module 30 in which a battery 31 in which a charging/discharging capacity is likely to decrease due to an influence of a memory effect (for example, a nickel-hydride battery or a nickel-cadmium battery) is used out of a plurality of battery modules 30.

<Power Supply Control Process Routine>

In a power supply control process routine, refreshing charging/discharging is performed on certain battery modules 30 in a string 10 in a state in which sweep control is being executed in the string 10. The power supply control process routine which is performed by the power supply system 1 according to this embodiment will be described below with reference to FIG. 5.

The power supply control process routine which is described in this embodiment is performed by the SCU 11 which is a controller (a control unit) of the string 10. When a sweep control start instruction in the string 10 is input from the GCU 2, the

SCU 11 starts the power supply control process routine illustrated in FIG. 5. The controller that performs the power supply control process routine is not limited to the SCU 11. For example, the GCU 2 may perform the power supply control process routine or a controller that performs the power supply control process routine may be provided separately from the SCU 11 and the GCU 2. A plurality of controllers (for example, the SCU 11 and a plurality of sweep units 50) may perform the power supply control process routine in cooperation with each other.

When the power supply control process routine is started, the SCU 11 determines which of discharging of electric power to the power distribution device 5 (that is, outputting of electric power to the outside) and charging with electric power supplied from the power distribution device 5 (that is, inputting of electric power from the outside) is instructed to be performed (S1). An instruction signal for performing one of discharging and charging is input to the SCU 11 from the GCU 2 which is a host controller. The SCU 11 determines which of discharging and charging is instructed to be performed in accordance with the input instruction signal.

When discharging is instructed to be performed (S1: YES), the SCU 11 performs a process associated with refreshing discharging while discharging instructed electric power from the string 10 to the power distribution device 5 (S3 to S9). First, the SCU 11 outputs the forcible connection signal CCS to a sweep module 20 in which a battery module 30 which is to perform refreshing discharging (a refreshing module) is provided out of a plurality of sweep modules 20 in the string 10 (S3). The refreshing module which is to perform refreshing discharging is appropriately determined by the SCU 11 as described above. When the process of S3 is performed, the refreshing module which is to perform refreshing discharging is kept connected to the main line 7. As a result, refreshing discharging of the refreshing module is appropriately performed.

Then, the SCU 11 outputs the forcible through signal CSS to a sweep module 20 in which a battery module 30 which is to perform refreshing charging (a refreshing module) is provided out of the plurality of sweep modules 20 in the string 10 (S4). The refreshing module which is to perform refreshing charging is appropriately determined by the SCU 11 as described above. When the process of S4 is performed, the refreshing module which is to perform refreshing charging is disconnected (separated) from the main line 7. As a result, electric power of the refreshing module which is to perform refreshing charging is not discharged but is maintained.

The SCU 11 sets conditions of sweep control (S5). A VH command signal for indicating a voltage VH which is output to the power distribution device 5 is input to the SCU 11 from the GCU 2 which is a host controller. As described above, the SCU 11 sets conditions of sweep control such as a delay time DL and a period T of a gate signal GS based on a VH command value indicated by the VH command signal, the voltage Vmod of each battery module 30, the number P of sweep modules 20 which are to be connected to the main line 7, and the like. The SCU 11 excludes a refreshing module to which the forcible connection signal CCS or the forcible through signal CSS is output in S3 and S4 from connection objects which are to be connected to the main line 7 in sweep control and sets the sweep conditions.

The SCU 11 starts sweep control based on the sweep conditions set in S5 (S6). As a result, sweep control is executed in a state in which the refreshing module has been excluded. That is, in a state in which electric power is being normally output from the plurality of sweep modules 20 to the outside, refreshing charging/discharging is appropriately performed on certain refreshing modules.

Subsequently, the SCU 11 determines there is a battery module 30 in which refreshing discharging has been completed (S8). The SCU 11 determines whether refreshing discharging in a battery module 30 (a refreshing module) has been completed based on a variety of information (for example, at least one of a calculated value of an amount of electric power cumulatively discharged from the battery module 30 and the voltage of the battery module 30). When there is a battery module 30 in which refreshing discharging has been completed (S8: YES), the SCU 11 performs a process of stopping a forcible connection operation on the sweep module 20 including the battery module 30 in which refreshing discharging has been completed (S9). As a result, refreshing discharging is stopped.

The process which is performed on the sweep module 20 in which refreshing discharging has been stopped can be appropriately selected. For example, in this embodiment, the SCU 11 outputs the forcible through signal CSS to the sweep module 20 in which refreshing discharging has been stopped and disconnects the sweep module 20 from the main line 7 until charging of the battery module 30 is performed the next time.

Subsequently, the SCU 11 performs various processes (S19). For example, when the VH command value which is output to the power distribution device 5 is changed, the SCU 11 resets the conditions of sweep control based on the changed VH command value. Subsequently, the SCU 11 determines whether an instruction to end sweep control has been input (S20). When an ending instruction has not been input (S20:

NO), the process routine returns to 51 and sweep control is continuously performed. When a discharging command is continuously output, the processes of S3 to S20 are repeatedly performed. When the discharging command is changed to a charging command, the processes of S11 to S20 are performed. When the ending instruction has been input (S20: YES), the power supply control process routine ends.

When the charging command has been input (S1: NO), the SCU 11 performs a process associated with refreshing charging while performing normal charging based on sweep control on a plurality of battery modules 30 (S11 to S17). First, the SCU 11 outputs the forcible connection signal CCS to a sweep module 20 in which a battery module 30 which is to perform refreshing charging (a refreshing module) is provided out of the plurality of sweep modules 20 in the string 10 (S11). The refreshing module which is to perform refreshing charging is appropriately determined by the SCU 11 as described above. When the process of S11 is performed, the refreshing module which is to perform refreshing charging is kept connected to the main line 7. Electric power is input to the main line 7 from the power distribution device 5. As a result, refreshing charging on the refreshing module is appropriately performed.

Subsequently, the SCU 11 outputs the forcible through signal CSS to the sweep module 20 in which a battery module 30 which is to perform refreshing discharging (a refreshing module) is provided out of the plurality of sweep modules 20 in the string 10 (S12). When the process of S12 is performed, the refreshing module which is to perform refreshing discharging is disconnected from the main line 7. As a result, the refreshing module which is to perform refreshing discharging is kept not charged.

The SCU 11 sets conditions of sweep control (S13). Here, the SCU 11 excludes a refreshing module to which the forcible connection signal CCS or the forcible through signal CSS has been output in S11 and S12 from connection objects which are to be connected to the main line 7 in sweep control and sets the sweep conditions.

The SCU 11 starts sweep control based on the sweep conditions set in S13 (S14). As a result, sweep control is executed in a state in which the refreshing module has been excluded. That is, refreshing charging/discharging on some refreshing modules is appropriately performed in a state in which charging of the plurality of sweep modules 20 is normally being performed.

Subsequently, the SCU 11 determines whether there is a battery module 30 in which refreshing charging has been completed (S16). The SCU 11 determines whether refreshing charging of a battery module 30 (a refreshing module) has been completed based on a variety of information (for example, at least one of a calculated value of an amount of electric power with which the battery module 30 has been cumulatively charged and the voltage of the battery module 30). When there is a battery module 30 in which refreshing charging has been completed (S16: YES), the SCU 11 performs a process of stopping a forcible connection operation on the sweep module 20 including the battery module 30 in which refreshing charging has been completed (S17). As a result, refreshing charging is stopped.

The process which is performed on the sweep module 20 in which refreshing charging has been stopped can be appropriately selected. For example, in this embodiment, the SCU 11 outputs the forcible through signal CSS to the sweep module 20 in which refreshing charging has been stopped and disconnects the sweep module 20 from the main line 7 until a discharging command for the string 10 is input the next time.

Thereafter, the process routine progresses to S19 and S20. When a charging command is continuously output, the processes of S11 to S20 are repeatedly performed. When the charging command is changed to a discharging command, the process routine progresses to S3 to S20. When an ending instruction is input (S20: YES), the power supply control process routine ends.

The process of executing sweep control in S6 and S14 in FIG. 5 is an example of a “first process.” The process of maintaining connection of a refreshing module to the main line 7 during execution of sweep control in S3, S5, S6, S11, S13, and S14 in FIG. 5 is an example of a “second process.”

While a specific embodiment of the disclosure has been described above in detail, the embodiment is only an example and does not limit the appended claims. The technique described in the claims includes various modifications and changes of the above-mentioned embodiment. 

What is claimed is:
 1. A power supply system comprising: a main line that supplies electric power which is output to the outside and electric power which is input from the outside; a plurality of sweep modules that is connected to the main line; and a control unit, wherein each sweep module includes a battery module that includes at least one battery, and a power circuit module that includes at least one switching element that switches between connection and disconnection between the battery module and the main line, and wherein the control unit is configured to perform a first process of executing sweep control for sequentially switching the battery modules which are to be connected to the main line out of the plurality of battery modules by outputting a gate signal for controlling the switching element to the power circuit module, and a second process of maintaining connection between a refreshing module which is a battery module in which an influence of a memory effect of the battery is to decrease and the main line while performing sweep control in a state in which the refreshing module is excluded in at least one of outputting of electric power to the outside via the main line and inputting of electric power from the outside via the main line.
 2. The power supply system according to claim 1, wherein the control unit is configured to execute the sweep control in a state in which the refreshing module in which a state of charge of the battery is increased to a state of charge with which an influence of a memory effect decreases is disconnected from the main line during outputting of electric power to the outside via the main line.
 3. The power supply system according to claim 1, wherein the control unit is configured to execute the sweep control in a state in which the refreshing module in which a state of charge of the battery is decreased to a state of charge with which an influence of a memory effect decreases is disconnected from the main line during inputting of electric power from the outside via the main line.
 4. The power supply system according to claim 1, wherein the at least one switching element of the power circuit module includes: a first switching element that is attached in series to the main line and in parallel to the battery module; and a second switching element that is provided in a circuit that connects the battery module in series to the main line, and wherein the control unit is configured to execute the sweep control by sequentially outputting the gate signal for controlling alternate driving of ON and OFF of the first switching element and the second switching element to a plurality of sweep modules which is to be connected to the main line out of the plurality of sweep modules at intervals of a predetermined delay time, output a signal for maintaining an OFF state of the first switching element and an ON state of the second switching element to the sweep module including the refreshing module when connection of the refreshing module to the main line is maintained, and output a signal for maintaining the ON state of the first switching element and the OFF state of the second switching element to the sweep module including the refreshing module when the refreshing modules is disconnected from the main line. 